The fastest useful split
Exit-hole diameter and frass texture are decisive: powderpost signs are tiny and flour-like; old-house-borer signs are larger and coarser.
Do not rely on a single color match. Start with scale and physical form, then check where the sign accumulates and whether a companion clue supports one candidate over the other.
| Feature | Powderpost beetle | Old house borer |
|---|---|---|
| Hole | Tiny round | Larger oval |
| Frass | Fine powder | Coarse packed material |
| Wood | Often hardwood/sapwood | Seasoned softwood framing |
| Sound | Usually unnoticed | Possible feeding noise |
Measure several holes and identify the affected wood.
Do not cut structural framing.
Open safety guidanceCheck each full evidence profile
Powderpost beetle
Lyctinae and related groups
Tiny round holes with flour-like powder accumulating below unfinished or stored wood.
Old house borer
Hylotrupes bajulus
Larger oval exit holes, coarse packed frass and feeding sounds in softwood framing.
Why a visual match can fail
Scale can be distorted by a close-up photograph, loose material may be moved by cleaning or airflow, and old evidence can change color or texture. A reliable conclusion uses multiple observations that point in the same direction and preserves contradictory details instead of forcing a match.